Fix alignment issue with small mobile

- Use ems
- Remove 4px padding-bottom
Merge pull request #97 from sharetribe/contact-author-button

[Pending merge] Contact author button
Merge pull request #98 from sharetribe/no-photo-or-description

[Pending merge] No photo or description
Merge pull request #99 from sharetribe/show-map

Show map
Merge branch 'develop' into fix-listing-tests